Physikalisch-Technische Bundesanstalt, Braunschweig, Germany.
JILA, Boulder, CO, USA.
Nature. 2019 Mar;567(7747):204-208. doi: 10.1038/s41586-019-0972-2. Epub 2019 Mar 13.
Questioning basic assumptions about the structure of space and time has greatly enhanced our understanding of nature. State-of-the-art atomic clocks make it possible to precisely test fundamental symmetry properties of spacetime and search for physics beyond the standard model at low energies of just a few electronvolts. Modern tests of Einstein's theory of relativity try to measure so-far-undetected violations of Lorentz symmetry; accurately comparing the frequencies of optical clocks is a promising route to further improving such tests. Here we experimentally demonstrate agreement between two single-ion optical clocks at the 10 level, directly validating their uncertainty budgets, over a six-month comparison period. The ytterbium ions of the two clocks are confined in separate ion traps with quantization axes aligned along non-parallel directions. Hypothetical Lorentz symmetry violations would lead to periodic modulations of the frequency offset as the Earth rotates and orbits the Sun. From the absence of such modulations at the 10 level we deduce stringent limits of the order of 10 on Lorentz symmetry violation parameters for electrons, improving previous limits by two orders of magnitude. Such levels of precision will be essential for low-energy tests of future quantum gravity theories describing dynamics at the Planck scale, which are expected to predict the magnitude of residual symmetry violations.
对空间和时间结构的基本假设提出质疑，极大地增强了我们对自然的理解。最先进的原子钟使得精确测试时空的基本对称性质以及在仅几个电子伏特的低能量下寻找超越标准模型的物理成为可能。现代对爱因斯坦相对论的测试试图测量迄今为止尚未检测到的洛伦兹对称性违反；准确比较光学时钟的频率是进一步改进此类测试的有前途的途径。在这里，我们通过长达六个月的比较实验，在 10 的水平上直接验证了两个单离子光学时钟之间的一致性，直接验证了它们的不确定度预算。两个时钟的镱离子被限制在单独的离子阱中，量子化轴沿着非平行方向排列。假设的洛伦兹对称性违反将导致频率偏移的周期性调制，因为地球绕太阳旋转和轨道运行。从 10 的水平上没有这种调制，我们推断出电子的洛伦兹对称性违反参数的严格限制约为 10，比以前的限制提高了两个数量级。这种精度水平对于未来描述普朗克尺度动力学的量子引力理论的低能测试至关重要，预计这些理论将预测剩余对称性违反的幅度。
